The 28-year-old triumphed 7-5, 7-6 (8-6), 3-6, 4-6, 6-3 after four hours and 54 minutes in Birmingham, giving the hosts an unassailable 3-1 lead in the best-of-five tie. 

Murray, the Australian Open runner-up, edged the first two sets before seemingly running out of steam in his first event back since the birth of his daughter.

Nishikori, ranked sixth in the world, fired a superb backhand winner to take the third set and served out the fourth at the second attempt as he threatened to become only the second man to recover from two sets down against Murray.

A break at the start of the fifth had the Japanese sensing victory, but Murray dug deep to turn the match back in his favour.

A forehand winner saw the Scot claim the last of five breaks in the opening six games to go 4-2 ahead, and he then held to move to within one game of victory.

Murray failed to convert two match points on the Nishikori serve, but he soon served out the victory to maintain his record of having never lost a Davis Cup singles match on a hard court in 13 outings.

"I was a little bit calmer in the fifth set," said Murray.

"I was panicking a little bit at the end of the third when I was struggling physically - I didn't quite know what to do.

"Last year was incredible every time I played in the Davis Cup.

"This team did something special and I would like to do the same again this year."

Awaiting Britain in the quarter-finals is Serbia, who overturned a 2-1 deficit to beat Kazakhstan 3-2.

World number one Novak Djokovic came from behind to claim a 6-7(6), 7-6(3), 4-6, 6-3, 6-2 victory over Mikhail Kukushkin and level the tie.

The turnaround was complete when Viktor Troicki breezed to a 6-2, 6-3, 6-4 success against Aleksandr Nedovyesov.

Elsewhere, John Isner secured the United States’ passage to the quarter-finals after stemming a fightback from Australian number one Bernard Tomic to win 6-4, 6-4, 5-7, 7-6(4) in Melbourne and seal a 3-1 win.

Victory, achieved through Isner’s 49th ace of the match, marked a first win for the Americans over Australia since 1997 and first Down Under since 1982.

Argentina needed one more point to take an unassailable lead against an injury-ravaged Polish side in Gdańsk.

Leonardo Mayer stepped up to deliver, fighting his way past a stubborn Michal Przysiezny 6-7(4), 7-6(4), 6-2, 6-3 to notch his 11th successive victory in his country’s colours.

It meant Hubert Hurkacz's 4-6, 7-6(6), 6-4 win against Renzo Olivo later in the day was no more than a consolation for Poland as the tie ended 3-2 in Argentina's favour. 

Czech Republic and Croatia were both pegged back to 2-2 in their respective ties against Germany and Belgium, but won the ensuing deciders to advance to the last eight.

Italy and France had already secured their quarter-final berths at the expense of Switzerland and Canada, and sealed 5-0 victories today. 

The quarter-finals, which are scheduled to take place from July 15 to 17, will see Serbia entertain Britain, Argentina travel to Italy, Czech Republic play host to France and Croatia head to the US.